An apparatus for actuating a droplet comprises a first conductive layer, a second conductive layer, a conductive elongate element, and a
voltage source. The first conductive layer comprises a first hydrophobic surface. The second conductive layer comprises a hydrophilic surface facing the first hydrophobic surface. The second conductive layer is axially spaced from the first conductive layer to define a gap therebetween. The conductive medial element is disposed in the gap between the first and second conductive
layers, and comprises a second hydrophobic surface. The
voltage source communicates with the second conductive layer and the elongate element. By applying a
voltage potential between the elongate element and the second conductive layer, droplets can be electrostatically actuated so as to move from the first conductive layer into contact with the second conductive layer. The apparatus is particularly useful in the synthesis of microarrays of biological, chemical, or biochemical samples.